1. Field of the Invention
The present invention relates to a level shift circuit, and more particularly, to the level shift circuit that has a low power dissipation and is realized in a more simplified way.
2. Description of Related Art
As shown in FIG. 1, one integrated circuit (IC) could exist different supply voltages for different applications, a level shift circuit 100 is required between two circuitries with different supply voltages to adjust the level of logic signals so as to maintain the normal operation of the circuitry. FIG. 2 is a diagram showing the signal relation between an input signal S1 and an output signal S2 of the level shift circuit 100 in FIG. 1. As shown in FIG. 2, after the output signal S2 passes the level shift circuit 100, its logic value does not change, but its voltage level is different. The voltage level of VH1 is shifted to the voltage level of VH2, and the voltage level of VL1 is shifted to the Voltage level of VL2.
In U.S. Pat. Nos. 5,057,721, 5,351,182, 6,362,679, 6,362,831 and 6,501,321, a level shift circuit making use of current and resistance to generate levels is disclosed. The level shift circuit using this method to generate levels will consume a large amount of power and require a complicated circuit to ensure the reliability and performance.
Besides, U.S. Pat. No. 6,476,672 discloses a level shift circuit of low power dissipation, high reliability and high performance, but it needs to generate four complicated control signals to achieve the function of level shifting.